What is a leap year?

A leap year is a calendar year containing an additional day added to keep the calendar year synchronized with the astronomical year. In the Gregorian calendar, a leap year has 366 days instead of the usual 365 days, with the extra day added as February 29th.

The Earth takes approximately 365.25 days to orbit the Sun. Without leap years, our calendar would gradually drift out of alignment with the seasons. By adding an extra day every four years, we compensate for this fractional difference and keep our calendar accurate.

Why do we need leap years?

The Earth's orbit around the Sun takes 365 days, 5 hours, 48 minutes, and 46 seconds. To account for these extra hours, we add one day every four years. However, this isn't quite exact, so there are exceptions: years divisible by 100 are not leap years unless they're also divisible by 400. This rule keeps our calendar aligned with Earth's orbit around the Sun.

Tool description

This leap year calculator instantly determines whether any given year is a leap year or not. Use this free leap year checker online to verify any year from the past, present, or future. Simply enter a year, and the tool automatically calculates whether it follows the leap year rules according to the Gregorian calendar system.

Features

  • Instant leap year calculator: Results appear instantly as you type the year
  • Clear visual feedback: Color-coded alerts show leap years (green) vs non-leap years (red)
  • Educational explanation: Learn the rule behind leap year determination
  • Check leap year online: Verify any year from 1 onwards, completely free
  • International support: Available in multiple languages

Use Cases

  • Event planning: Use this leap year checker to determine if an event year will have an extra day in February
  • Birthday checking: Find out if someone born on February 29th will have a birthday
  • Historical research: Check leap year dates online for historical timelines
  • Programming validation: Test and determine leap year logic in date-related software
  • Calendar creation: Ensure accurate calendar layouts for any year
  • Age calculations: Account for leap days when calculating precise ages

How the leap year rule works

A year is a leap year if:

  • It is divisible by 4, AND
  • It is NOT divisible by 100, UNLESS
  • It is also divisible by 400

Examples:

  • 2024 is a leap year (divisible by 4, not by 100)
  • 2000 was a leap year (divisible by 400)
  • 1900 was not a leap year (divisible by 100, but not by 400)
  • 2100 will not be a leap year (divisible by 100, but not by 400)